This invention relates to an improved electric motor structure and method of assembling the same and more particularly to an improved structure and method for securing a bearing support end shield to the stator assembly of an electric motor, for example, a fractional horsepower electric motor.
An electric motor, such as a fractional horsepower motor known in the art, generally includes a stator assembly of a stack of laminations (preferably made of sheets of suitable steel or other ferro-magnetic material) punched or stamped with a central bore and a plurality of winding receiving slots extending generally radially outwardly from the bore. The laminations are stacked to form a stator core and secured together in one or more of several ways including welding, epoxy adhesive and fastener cleats. A rotor assembly including a rotor body and an axial shaft extending therefrom is centered in the central bore of the stator core with a uniform air gap therebetween with the rotor shaft extending centrally from the rotor body end. Bearing support end shield means is secured to the stator assembly so that the rotor shaft is rotatably journalled in the bearing support to rotatably support the rotor body within the stator core assembly.
A number of assembly structures for securing the bearing support end shield means to the stator assembly have been employed in the art. The more recently issued U.S. Pat. Nos. 4,306,168 and No. 4,361,953 to C. Theodore Peachee on Dec. 15, 1981 and Dec. 7, 1982, respectively teach a novel apparatus and method for securing bearing support end shields to the stator assembly of an electric motor by utilizing self-tapping screws and removable shims during assembly operations.
The present invention, recognizing the advantageous features taught by these aforementioned patents, as well as certain of the limitations, provides an improved apparatus and method for securing bearing support end shield means to the stator core assembly of an electric motor which utilizes such past advantageous features combined with unique and novel additional structural features and method steps, which new structure and steps are low in cost in manufacture and assembly and which further enhance structural stability and balanced support of an assembled electric motor without special parts or expensive, complex processing steps and without jeopardizing the overall strength of the electric motor. In accordance with the present invention, a novel electric motor is provided which not only is economical in manufacture and assembly, but which is sturdy and stable with enhanced squareness and balance necessary for the rotor shaft ball bearings when operated under high loads and/or high speeds so as to extend motor life. This enhanced squareness is obtained in an economical and straightforward structure and method substantially less complex than past arrangements for squaring rotor shaft ball bearings.
Various other features of the present invention will become obvious to one skilled in the art upon reading the disclosure set forth herein.